[sdiy] My New Project - PCSYNTH

[Scott Gravenhorst]

Rainer Buchty <rainer at buchty.net> wrote:
>>Much of the amount of time it takes to simply toggle an LPT port bit comes
>>from the 'out' instruction, it seems to take about 1.5 uS on this CPU. 
>
>Hmmm, why not just bitbang an average soundcard or go for an ISA-bus 
>based DAC? That would spare you the wait states for accessing 
>the LPT port. 

A couple of reasons.  I'm trying not to buy _anything_.  A standard
soundblaster compatible (or soundblaster) does not give direct access to the
DAC.  The DAC is operated only by DMA in these.  There are other sound cards
that do allow this, but I don't have one (and again, I'm trying to this with
what otherwise would be landfill material).  The one card I saw that does
this was priced at US$50.00  An ISA-bus based DAC would probably suffer from
the same slow X86 "out" instruction (if it's a port, it's got to use an
"out"), so there would be little advantage other than it's already built. 
ISA rarity is also a problem and an ISA buss DAC is probably not easily
obtained either.

>
>Thinking of formats like S3M and XM even old 486 PCs should be able to 
>play back ~32 voices (and have enough horsepower left to render nice 
>demos like Future Crew's "2nd Reality").
>
>If you reduce it to e.g. 16 voices (or go for a faster machine) then 
>sufficient computing power for modulation/filtering should be there.

At this point, my plan is to put together a monosynth that can do things my
other digital synths don't.  Portamento is one, noise modulation of pitch is
another.


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-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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